7,951 research outputs found
Top effective operators at the ILC
We investigate the effect of top trilinear operators in t tbar production at
the ILC. We find that the sensitivity to these operators largely surpasses the
one achievable by the LHC either in neutral or charged current processes,
allowing to probe new physics scales up to 4.5 TeV for a centre of mass energy
of 500 GeV. We show how the use of beam polarisation and an eventual energy
upgrade to 1 TeV allow to disentangle all effective operator contributions to
the Ztt and gamma tt vertices.Comment: LaTeX 13 pages. Typos corrected. Final version in JHE
Top effective operators at the ILC
We investigate the effect of top trilinear operators in t tbar production at
the ILC. We find that the sensitivity to these operators largely surpasses the
one achievable by the LHC either in neutral or charged current processes,
allowing to probe new physics scales up to 4.5 TeV for a centre of mass energy
of 500 GeV. We show how the use of beam polarisation and an eventual energy
upgrade to 1 TeV allow to disentangle all effective operator contributions to
the Ztt and gamma tt vertices.Comment: LaTeX 13 pages. Typos corrected. Final version in JHE
Generation of maximally entangled states of qudits using twin photons
We report an experiment to generate maximally entangled states of
D-dimensional quantum systems, qudits, by using transverse spatial correlations
of two parametric down-converted photons. Apertures with D-slits in the arms of
the twin fotons define the qudit space. By manipulating the pump beam correctly
the twin photons will pass only by symmetrically opposite slits, generating
entangled states between these differents paths. Experimental results for
qudits with D=4 and D=8 are shown. We demonstrate that the generated states are
entangled states.Comment: 04 pages, 04 figure
Recent studies of top quark properties and decays at hadron colliders
The top quark is the heaviest known elementary particle. Observed for the
first time in 1995 at the Tevatron by the CDF and D0 experiments, it has become
object of several studies aimed at fully characterize its properties and
decays. Precise determinations of top quark characteristics verify the internal
consistency of the standard model and are sensitive to new physics phenomena.
With the advent of the large top quark production rates generated at the LHC,
top quark studies have reached unprecedented statistical precision. This review
summarizes the recent measurements of top quark properties and studies of its
decays performed at the LHC and Tevatron.Comment: 13 pages, 4 figures, 5 tables, Presented at Flavor Physics and CP
Violation (FPCP 2012), Hefei, China, May 21-25, 201
Propagation of spatially entangled qudits through free space
We show the propagation of entangled states of high-dimensional quantum
systems. The qudits states were generated using the transverse correlation of
the twin photons produced by spontaneous parametric down-conversion. Their
free-space distribution was performed at the laboratory scale and the
propagated states maintained a high-fidelity with their original form. The use
of entangled qudits allow an increase in the quantity of information that can
be transmitted and may also guarantee more privacy for communicating parties.
Therefore, studies about propagating entangled states of qudits are important
for the effort of building quantum communication networks.Comment: 5 Pages, 4 Figures, REVTeX
A clean signal for a top-like isosinglet fermion at the Large Hadron Collider
We predict a clean signal at the Large Hadron Collider (=14 TeV for
a scenario where there is a top-like, charge +2/3 vectorlike isosinglet
fermion. Such a quark, via mixing with the standard model top, can undergo
decays via both flavour-changing Z-boson coupling and flavour-changing Yukawa
interactions. We concentrate on the latter channel, and study the situation
where, following its pair-production, the heavy quark pair gives rise to two
tops and two Higgs boson. We show that the case where each Higgs decays in the
channel, there can be a rather distinct and background-free signal
that can unveil the existence of the vectorlike isosinglet quark of this kind.Comment: 14 pages, 5 figures, 4 table
Long-distance distribution of genuine energy-time entanglement
Any practical realization of entanglement-based quantum communication must be
intrinsically secure and able to span long distances avoiding the need of a
straight line between the communicating parties. The violation of Bell's
inequality offers a method for the certification of quantum links without
knowing the inner workings of the devices. Energy-time entanglement quantum
communication satisfies all these requirements. However, currently there is a
fundamental obstacle with the standard configuration adopted: an intrinsic
geometrical loophole that can be exploited to break the security of the
communication, in addition to other loopholes. Here we show the first
experimental Bell violation with energy-time entanglement distributed over 1 km
of optical fibers that is free of this geometrical loophole. This is achieved
by adopting a new experimental design, and by using an actively stabilized
fiber-based long interferometer. Our results represent an important step
towards long-distance secure quantum communication in optical fibers.Comment: 6 pages, 3 figures. Matches published versio
Short-range correlations in low-lying nuclear excited states
The electromagnetic transitions to various low-lying excited states of 16O,
48Ca and 208Pb are calculated within a model which considers the short-range
correlations. In general the effects of the correlations are small and do not
explain the required quenching to describe the data.Comment: 6 pages, 2 postscript figures, 1 tabl
- …